Circuit breaker



Dec. 22, 1959 E. A. LINK 2,918,557

CIRCUIT BREAKER Filed May 15, 1958 3 Sheets-Sheet 1 FIE-.1

INV EN TOR.

Edwin A.LJJ.7ZI

A hormgy Dec. 22, 1959 E. A. LINK CIRCUIT BREAKER 3 Sheets-Sheet 2 Filed May 15, 1958 Pic-=5 United States Patent CIRCUIT BREAKER Edwin A. Link, Waukesha, Wis., assignor to R T & E

Corporation, Waukesha, Wis., a corporation of Wisconsln Application May 15, 1958, Serial No. 735,541

12 Claims. (Cl. 200-129) This invention relates to a circuit breaker of the internal bayonet oil type adapted to protect a piece of electrical apparatus from damage caused by overload or load short circuits.

To the best of my knowledge, similar devices have been incorporated in a high potential terminal bushing of a transformer. This type of circuit breaker mounting has not proved to be entirely satisfactory, in use, by reason of the fact that the circuit breaker could not be inserted or removed except by the use of a hot stick because of the high line voltage at the terminal bushing. Furthermore, this type of circuit breaker mounting permits the overflow of oil from the tank when the circuit breaker is removed from the terminal bushing as a result of the internal pressure developed in the transformer when the fuse element blows. A further disadvantage of this type of circuit breaker mounting lies in the fact that the high internal pressure caused by the blowing of the fuse in the transformer tank is of suflicient magnitude to forcibly eject the bayonet fuse from the terminal bushing immediately upon the release of latching pressure between the bayonet fuse and its cooperating terminal bushing.

The primary object of the invention resides in the independent mounting of a bayonet type oil circuit breaker in a manner such that it forms no part of the high potential terminal bushing of the apparatus.

Another object resides in the provision of a bayonet type oil circuit breaker provided with an operating handle maintained at the tank potential so that the device may be manually inserted into or removed from the tank without the aid of the hot stick or the encountering of high line voltage.

A further object resides in the provision of a bayonet type oil circuit breaker which is vented to relieve the internal pressure in the tank immediately upon the release of the latching engagement between the bayonet circuit breaker and its receptacle to thereby preclude both the forceful ejection of the circuit breaker from the tank or the loss of oil from the tank as a result of the internal pressure built up by the blowing of the fuse.

Another object resides in the provision of an internal bayonet type oil circuit breaker having a pair of spaced electrical contact elements submerged in the dielectric fluid contained in the casing and a bridging contact member on the bayonet portion of the device adapted to establish the electrical connection between the spaced contacts when the bayonet portion of the device is in operating position.

Another object of the invention resides in the provision of a resilient deformable sleeve member adapted to provide an hermetic seal for the opening through which the bayonet portion of the circuit breaker is in sertible.

Another object resides in the provision in a bayonet type oil circuit breaker of means for transmitting the 2,918,557 Patented Dec. 22, 1959 increased air pressure in the casing, caused by the rupture of a fuse, to the inner surface of the deformable resilient sleeve to insure its effectiveness to maintain the hermetic seal in spite of greatly increased pressure within the casing.

Another object resides in the provision within a bayonet type oil circuit breaker of venting means to provide a balanced pressure on the bayonet portion of the circuit breaker to preclude its forceful ejection from the tank and the loss of dielectric fluid upon the breaking of the hermetic seal between the bayonet portion of the circuit breaker and its receptacle.

Another object resides in the provision of a bayonet type oil circuit breaker that may selectively serve with equal facility as a switch or fuse.

Other objects will become apparent from the following description of illustrative embodiments of the present invention.

In the drawing:

Figure 1 illustrates a circuit breaker, constructed in accordance with the teachings of the present invention, applied to a piece of electrical apparatus, such as a transformer, for the purpose of affording protection to the apparatus;

Fig. 2 is a fragmentary elevational view of a portion of the transformer casing and the upper portion of the circuit breaker;

Fig. 3 is a view similar to that shown in Fig. 2 taken from within the transformer casing;

Fig. 4 is a horizontal sectional view, taken substantially on the line 44 of Fig. 3, showing the internal mounting means for retaining the circuit breaker in fixed sealing position on the transformer casing;

Fig. 5 is a vertical longitudinal sectional view taken substantially on the line 55 of Fig. 2, showing the insertible bayonet portion of the circuit breaker in elevation and in unlatched position with its cooperating support and fusing means shown in section;

Fig. 6 is a view similar to Fig. 5 wherein the insertible bayonet portion of the circuit breaker is shown in its latched operating position wherein it completes the electrical circuit between spaced terminals carried by the support for the bayonet portion of the device;

Fig. 7 is a fragmentary elevational view of the bottom portion of the circuit breaker showing resilient means for normally maintaining a pair of slidably mounted electrical contacts in position to establish an electrical connection with electrical contacts carried by the insertible bayonet portion of the circuit breaker when it is in operating position;

Fig. 8 is a horizontal sectional view, taken substantially on the line 88 of Fig. 7, showing the cooperating relationship between a pair of associated contacts of the device;

Fig. 9 is an enlarged vertical sectional view of the upper part of the insertible bayonet portion of the circuit breaker, taken substantially on the line 9-9 of Fig. 5, showing the structural arrangement of some of the associated elements which comprise the insertible bayonet portion of the circuit breaker;

Fig. 10 is an enlarged elevational view of the lower part of the insertible bayonet portion of the circuit breaker, with parts broken away to more clearly illustrate its structure and the mounting of a fusible element therein; and

Fig. 11 is a view similar to that shown in Fig. 10 wherein a non-fusible element is substituted for a fusible element shown in Fig. 10 to adapt the device for use as a switch.

Before entering into a detailed description of the illustrative embodiments of the internal bayonet type oil circuit breaker of the present invention, it is believed As previously stated, it has been a practice to embody a bayonet type circuit breaker or oil fuse in the high voltage line terminal bushing of a transformer. With the circuit breaker comprising a part of the terminal bushing of a transformer, it will be understood that a hook stick must, of necessity, be utilized in the application before removal of the bayonet type circuit breaker from the terminal bushing by reason of the presence of high voltage.

The present invention provides an independently mounted bayonet type oil circuit breaker having a manually operable means, at tank potential, to permit its ready application or removal without the possibility of encountering high voltages in so doing.

Referring more particularly to Fig. 1 of the accompanying drawing, it will be noted that an internal bayonet type oil circuit breaker 10, constructed in accordance with the teachings of the present invention, is applied to a transformer tank 11 which houses the usual corecoil assembly 12 of the-transformer. The transformer tank 11 is provided with a cover 13 on which a high voltage terminal bushing 14 is mounted. The internal terminal of the bushing 14 is connected by means of a flexible electrical connector 15 to one of a pair of electrical contacts of the circuit breaker 10 and the other electrical contact of the circuit breaker 10 is connected by means of the lead 16 to one terminal 17 of the corecoil 12. Another terminal 17' of the core-coil assembly 12 is connected to the transformer tank 11 by means of a lead 18 and the transformer tank 11 is grounded through a lead 19. From the above description, it will be noted that the circuit breaker 10 is connected in series between the high voltage terminal bushing 14 and the electrical apparatus, in the form of a core-coil 12 for which it forms a protective device. The transformer casing contains a sufficient quantity of dielectric fluid 20 to immerse the lower extremity of the high voltage terminal bushing 14, the spaced electrical contacts on the circuit breaker 10 and the core-coil assembly 12 so that the circuit breaker 10 comprises an oil type device.

The circuit breaker 10 extends through an opening 21 formed in the wall of the tank 10 and includes a tubular casting 22 provided with an axial bore 23 which extends the full length of the casting 22. The casting 22 is provided with an annular flange 24 which includes a shoulder 25 which delineates a circular projection 26 adapted to be slidably received through opening 21 formed in the tank 11. It should be noted at this time that the axis of the casting 22 and that of the shoulder 25 are disposed in annular relationship with each other so that the circuit breaker 10 extends inwardly and outwardly through the opening 21 in the tank to properly position its lower extremity below the level of dielectric fluid 20 contained in the tank 11. A sealing washer 27 surrounds the projection 26 and abuts the shoulder 25 to provide a seal for the joint between the circuit breaker 10 and the tank 11. The tubular casting 22 is releasably retained in fixed position on the tank 11 by means of a U-shaped strap 28 having laterally spaced legs 29 adapted to span the opening 21.

Clamping pressure is applied to the U-shaped strap 28 by the tightening of cap screws 30 which pass through holes 31 in the base of the U-shaped member 28 and threadedly received in tapped holes 32 formed in the projection 26 of the casting 22. The clamping pressure applied through the medium of the U-shaped member 28 serves to compress the sealing washer 27 between the shoulder 25 and the surface of the tank 11 surrounding the opening 21 to effectively seal the same.

A vent opening 33 provides for open communication between the interior of the tank 11 and the axial bore 23 formed in the tubular casting 22 for the purpose to be hereinafter more specifically described. The upper portion of the tubular member 34 formed of insulating material is slidably receivable in the axial bore 23 of the tubular casting 22 and is releasably retained in fixed position therein through the medium of a drift pin 35 which is positioned in the bore 36 formed in the boss 37 adjacent the lower end of the tubular casting 22. A pair of axially spaced upper and lower holes 38 and 39, respectively, serve to slidably receive identical cylindrical contact elements 40. Each of the contact elements 40 include a pair of axially spaced transversely extending inner and outer holes 41 and 42 respectively. A circular spring element 43 in the form of a clip is slidably receivable through the hole 41 of a pair of contacts 40 after they have been positioned in the axially spaced holes 38 and 39 to normally urge each pair of contacts 40 toward their innermost position in which their inner ends are disposed within an axial bore 44 formed in the tubular member 34. The outer hole 42 in each of the contacts 40 serve to selectively receive the ends of electrical wires which lead to and from contacts 40.

The operation of the circuit breaker, above described, comprises the support 23 adapted to slidably receive the removable bayonet portion of the circuit breaker 10.

The removable portion of the circuit breaker 10 comprises a tubular member 45 formed of insulating material having a diameter which is slidably receivable in the axial bore 44 of the member 34. The lower end of the tubular member 45 is of slightly reduced diameter and terminates at its upper end in the groove 46. A combined coupling and electrical contact element 47 has a diameter substantially equal to that of the tubular member 45 and is slidably receivable over the reduced lower end of the member 45 and is retained thereon by the rolling or crimping of its top marginal edge in the groove 46. An apertured partition 48 serves to properly position the coupling element 47 on the lower portion of the tubular member 45. The inner surface of the bottom portion of the coupling member 47 is provided with threads 49 adapted to receive the threaded upper extremity 50 of a second tubular member 51 also formed of insulating material. The lower portion of the member 51 is constructed in a manner similar to that described in connection with the lower extremity of tubular member 45. An electrical contact element 52 is applied to the lower extremity of the member 51 by sliding the same from the end of the tube 51 and rolling or crimping its upper marginal edge in an annular groove 53 formed at the upper end of a reduced diameter portion 54. The outside diameter of the electrical contact element 52 is substantially identical With the diameter of the tubular member 51 so as to provide a substantially continuous smooth outer surface for the circuit making and breaking portion of the removable bayonet part of the circuit breaker. The lower extremity of the electrical contact element 52 is preferably formed as a truncated cone 55 which serves to engage the inner ends of the several electrical contact elements 40 as the bayonet portion of the circuit breaker is inserted through the axial bores 23 of the tubular casting 22 and the axial bore 44 of the tubular member 34 to a position wherein the contact elements 47 and 42 respectively engage pairs of the electrical con- 7 tacts 40 which are slidably mounted in the axially spaced holes 38 and 39 of the tubular member 34. A plurality of tangs 56 are struck inwardly from the circumferential wall of the contact element 52 immediately above the adjacent conical portion 55 thereof. These tangs serve to position the contact element 52 on the member 51 and also provide openings through which a fuse link 57 may be threaded. A similar tang 58 is struck outwardly from the end surface of the conical portion 55 to facilitate the anchoring of the lower end of the fuse link 57 in position within the axial bore 59 of the member 51. The fuse link 57 comprises an electrical connector disposed between the contact elements 47 and 52. The fuse link 57 hasits upper extremity electrically connected to an eyelet 61) that includes an outwardly directed flange portion 61 adapted to be retained in electrical connection with the partioned portion 48 of the coupling and contact member 47 through pressure exerted by tightening the upper end of the tubular member 51 in the threaded portion of the coupling 47. Should it be necessary to replace the fusible link 57, the bayonet portion of the circuit breaker may be removed from its support and the tubular portion 51 thereof may be unscrewed from the coupling member 47 to permit the threading of a new fuse link through the axial bore 59 of the tube 51 and the drawing of the flange portion 61 of the eyelet 60 into surface contact with the upper end of the tubular member 51. The lower end of the fuse link 57 may then be threaded through the apertures formed by the tangs 56 to effect the desired electrical connection between the upper and lower contact elements 47 and 52 of the device.

Referring more particularly to Fig. 11 of the accompanying drawing, it will be noted that a hollow bridging contact member 62 has been substituted for the fuse link 57. The substitution of the bridging contact member 62, which is non-fusible in nature, provides a simple and effective means for utilizing the device as a switch without including the protective feature afforded by the use of the fuse link 57. The member 62 comprises a relatively thin walled tube formed of conducting material that is insertible in the axial bore 59 of the tubular member 51. The upper and lower extremities of the member 62 are spun outwardly in contact with the extremities of the member 51 to provide the required electrical connection between the ends of the members 62 and the associated electrical contacts 47 and 52' disposed at the opposite ends of the member 51. In the switch form of the device shown in Fig. 11 the contact element 52 is secured to the member 51 in the identical manner previously described in connection with the contact 52. However, it will be noted that the lower portion of the contact 52 includes an inwardly directed flange 63 and a downwardly directed tubular portion 64 which is provided with exterior threading 65 to permit the application of a tubular member 66 which is formed of insulating material. The purpose of applying the tubular member 66 below the electrical contact 52' is to provide a simple and effective means for quenching an are upon the withdrawal of the bayonet portion of the circuit breaker from its operating position wherein the axially spaced contacts 40 carried by the tubular member 34 are electrically connnected by the contacts 47 and 52' through the medium of the member 62.

Manually operable means is secured to the upper ex t'remity of the tubular member 34 for the purpose of facilitating its insertion or withdrawal from the tubular casting 22 and for affording means by which the bayonet portion of the circuit breaker 10 may be releasably retained in sealing contact with the opening of the casting 22 intowhich itis 'removably insertible.

Referring more particularly to Fig. 9 of the accompanying drawing, it will be noted that the upper end of the tubular member 45 is provided with threading 67 adapted to be received in the lower portion of the central threaded opening of a coupling member 68. A stud 69 provided with a lower threaded portion 70 is also threadedly received in the upper portion of the coupling and lowerportions of the member 45 and stud 69. A

jam nut75 is also threadedly received on the stud 69 and serves to adjustably regulate the pressure applied to a deformable resilient rubber sleeve element 76 which surrounds the stud 69- and is interposed between the jamon the stud 69. i A transversely extending hole 78 formed adjacent the upper extremity of the stud 69 serves to receive a pin 79 on which a bifurcated operating handle 80 be noted that the spaced legs of the bifurcated handle 80 which include a pair of flat cam surfaces 81 and 82 respectively connected by the arcuate surface 83. It should also be noted that the distance between the fiat cam surface 81 and the axis of the mounting pin 79 is considerably shorter than the distance between the flat cam surfaces 82 and the axis of the mounting pin 79. The position of the operating handle '80 shown in Fig. 5 illustrates the relative positioning between the associated elements when the device is in unsealed position and ready for insertion into or removal from the mounting casting 22. Referring more particularly to Fig. 6, it will be noted that the device as therein shown in a sealed operating position wherein the deformable resilient rubber sleeve element 76 has been compressed under the rocking action of the cam surfaces 82 to effect the expansion of the sleeve element into sealing contact with the axial bore 23 formed in the tubular casting 22. The operating handle also includes an opening 84 to afford a means by which the handle may be actuated either by manually gripping of the same or by the use of a hook stick. The operating handle 80 is also provided with a tongue 85 adapted to engage the under surface of a flange 86 formed on the upper end of the casting 22 to provide a means for releasably retaining the removable bayonet portion of the circuit breaker 10 in operating position within the casting 22.

While the mechanical pressure applied to the opposite ends of the deformable resilient rubber sleeve element 76 by the jam nut and the washer 77, under .the pivotal movement of the operating handle is sufficient to insure the sealing of the removable bayonet portion of the circuit breaker 10 in its supporting casting 22, it has been deemed expedient to augment this sealing pressure by utilizing the extremely high pressure built up in the sealed transformer tank 11. As previously stated, the members 45 and 5d of the removable bayonet por tion of the device are tubular in form so that open communication extends between the interior of the tank and the last mentioned tubular elements. In order to direct the internal pressure of the tank to the inner surface of the deformable resilient rubber sleeve element 76, an axial'passage 87 is formed in the stud 69 and a plurality of radial passages 88 extend transversely of the stud69 provide open communication between the passage 87 and the inner surface of the element 76. On occasions when the fusible element 57 ruptures, it is not infrequent to have a tremendous rise in gas pressure within the tank 11 which will approach 200 pounds per square inch. In view of the extremely high pressure developed at this time, it is deemed advisable to direct this pressure to the inner surface of the deformable resilient rubber sleeve element 76 in order to augment the'mechanical sealing pressure applied thereto to insure against the forceful ejection of the bayonet portion of the circuit breaker from its support. plished by means of the passages 86 and 88 which are in open communication with the interior of the tank 11 through the axial bores 44 and 59 in the tubular mem bers' 4'5 and 51'.

The vent opening 33 formed in the tubular casting 22 provides open communication between the interior of the tank 11 and the axial bore '23 formed in the casting 22 to balance the-pressure on the insertible bayonet portion of the circuit breaker.

'When it is desired to remove the bayonet portion of the circuit breaker 10, after rupture of the fusible element 5 7, the operating handle '80 swing from its latching position (shown in Fig. 6) to the unlatching position (shown in Fig. 5) wherein the mechanical sealing pres- This is accom-- sure applied to the deformable resilient rubber sleeve element 76 is relieved and the bayonet portion of the circuit breaker may be easily withdrawn without the resulting loss of dielectric fluid from the casing 11 by reason of the balanced pressure within the bore 23 of the casting 22 and the bore 44 in the tubular member 34.

From the foregoing detailed description of the illustrative embodiments of the present invention, it will readily be understood that a simple and effective internal bayonet oil type circuit breaker has been provided in the form of either a fusible link or switch element that includes manually operable means disposed externally of a dielectric fluid containing casing to afford ready accessibility for the insertion or removal of the circuit breaker. It should also be noted that the circuit breaker is mounted independently of the high potential terminal of the apparatus and that the operating handle of the insertible and removable bayonet portion of the circuit breaker is maintained at casing potential so that it may be manipulated manually without the aid of a hot stick due to its low potential. Another important feature of the present invention resides in the provision of venting means for precluding both the forceful ejection of the insertible bayonet portion of the device or the loss of dielectric fluid from the tank upon the release of sealing pressure between the bayonet portion of the device and its support. Another advantage of the device lies in the fact that it includes communicating passages adapted to transfer the high internal pressure of the casing, upon rupture of the fusible element, to augment the mechanical sealing pressure afforded between the insertible bayonet portion and its associated support. A still further advantage of the present device lies in the use of a deformable resilient rubber sleeve element which is mechanically actuated to insure the provision of an hermetic seal between the removable bayonet portion of the device and its support.

While the invention has been described in considerable detail in the foregoing specification, it is to be understood that various changes may be made in its embodiment without departing from or sacrificing any of the advantages hereinafter claimed.

I claim:

1. The combination with a piece of electrical apparatus including a dielectric fluid containing casing provided with a line terminal, of a bayonet type oil circuit breaker, said circuit breaker comprising a pair of cooperating elements one of which is a support fixedly positioned on the casing independently of the line terminal and the other of which is a bayonet assembly removably insertible into said support, an insulating element projecting from said support and having a portion thereof disposed below the level of fluid Within the casing, a pair of spaced electrical contacts on said insulating element disposed below the level of liquid in the casing and respectively electrically connected with the line terminal and the piece of electrical apparatus, said bayonet assembly comprising an insulating member, and a bridging electrical contact on said member, said bridging electrical contact serving to establish an electrical connection between said pair of spaced electrical contacts on said insulating element when said'bayonet assembly is in operating position within said support and serving to break the said electrical connection when said bayonet assembly is withdrawn from said support.

2. The combination with a piece of electrical apparatus including a dielectric fluid containing casing provided with a line terminal, of a bayonet type oil circuit breaker, said circuit breaker comprising a pair of cooperating elements one of which is a support fixedly positioned on the casing independently of said line terminal and the other of which is a bayonet assembly removably insertable into said support, said support having portions within and without the casing, the portion of said support within the casing comprising an element formed of insulating material projecting below the level of fluid within said casing, a pair of spaced electrical contacts on said element, said electrical contacts being disposed below the level of fluid in said casing respectively electrically connected with the line terminal and the piece of electrical apparatus, said bayonet assembly comprising an insulating member, and a bridging electrical contact on said member, said bridging electrical contact serving to establish an electrical connection between said pair of spaced electrical contacts on said support when said bayonet assembly is in operating position within said support and serving to break the electrical connection when said bayonet assembly is withdrawn from said support.

3. The combination with a piece of electrical apparatus including a dielectric fluid containing casing provided with a line terminal, of a bayonet type oil circuit breaker, said circuit breaker comprising a pair of cooperating elements one of which is a support fixedly positioned on the casing independently of the line terminal and the other of which is a bayonet assembly removably insertible into said support, said support having portions within and without the casing, the portion of said support disposed within the casing comprising a tubular element formed of insulating material projecting below the level of fluid in the casing, 21 pair of spaced contact receiving apertures in the wall of said tubular element disposed below the level of fluid in the casing, a pair of electrical contacts slidably receivable in said apertures and respectively electrically connected with the line terminal and the piece of electrical apparatus, and resilient means urging said contacts toward the axis of said tubular element, said bayonet assembly comprising an insulating member, and a bridging electrical contact on said member, said bridging electrical contact serving to establish an electrical connection between said pair of spaced electrical contacts on said tubular element when said bayonet assembly is in operating position within said support and serving to break the electrical connection when said bayonet assembly is withdrawn from said support.

4. The combination with a piece of electrical apparatus including a dielectric fluid containing casing provided with a line terminal, of a bayonet type oil circuit breaker, said circuit breaker comprising a pair of cooperating elements one of which is a support fixedly positioned on the casing independently of the line terminal and the other of which is a bayonet assembly removably insertible into said support, said support having portions within and without the casing, the portion within said casing comprising a tubular element formed of insulating material projecting below the level of fluid in the casing, a pair of spaced contact receiving apertures in the wall of said tubular element disposed below the level of fluid in the casing, a pair of electrical contacts slidably receivable in said apertures and respectively electrically connected with the line terminal and the piece of electrical apparatus, and resilient means urging said contacts toward the axis of said tubular element, said bayonet assembly comprising a tubular member formed of insulating material having a diameter which is slidably receivable within said tubular element, and a bridging electrical contact on said tubular member, said bridging electrical contact serving to establish an electrical connection between said pair of spaced electrical contacts on said tubular element when said bayonet assembly is in operating position within said support and serving to break the electrical connection when said bayonet assembly is withdrawn from said support.

5. The combination with a piece of electrical apparatus including a dielectric fluid containing casing provided with a line terminal, of a bayonet type oil circuit breaker, said circuit breaker comprising a pair of cooperating elements one of which is a support fixedly positioned on the casing independently of the line terminal and the other of which is a bayonet assembly removably insertible into said support, said support having portions 9 within and without the casing, the portion within said casing'comprising a tubular element formed of insulating material projecting below the level of fluid within said casing, a pair of spaced electrical contacts on said tubular element, said electricalcontacts being disposed below the 'level of ,fluid'in said casing and respectively electrically connected with the line terminal and the piece of electrical apparatus, said bayonet assembly comprising a tubular insulating member, slidably receivable in said tubular element, and a bridging electrical Contact on said tubular member, said bridging electrical contact serving to establish an electrical connection between said pair of spaced electrical contacts on said tubular member when said bayonet assembly is in operating position within said support-and serving to break the electrical connection when saidbayonet assembly is withdrawn from said support.

The combination with a piece of electrical apparatus'including a dielectric fluid containing casing providedwith a' line terminal, of a bayonet type oil circuit breaker, said circuit breaker comprising a pair of cooperating elements one of which is a tubular support fixedly positioned on the'casing independently of the line terminaland the other of which is a bayonet assembly removablyinsertibleinto said support, an insulating element projecting inwardly from said support and having a portion 'thereofdisposed belowthe level of fluid within thefcasing, a'pair of spaced electrical contacts on said insulating element disposed below the level of liqu'd in the casing and respectively electrically connected with the line'terminal and the pieceof electrical apparatus, a vent passage in said tubular supportdisposed above the level of fluid in'the casing serving to establish open communication' between the 'interior of the casing and the interior portion of said tubular support, said bayonet assembly comprising an insulating member, a pair of spaced electrical contacts on said member, a current carrying ele- ,ment'-con'necting said pair 'of electrical contacts on said member, andan operating handle on said bayonet assembly providing the means by which said bayonet assembly maybe inserted into or removed'from said support to effectfthe selective sealed closing and opening of the electricalcircuit between the pair of spaced electrical contacts on said insulating element, said vent passage serving to relieve the internal pressure in the casing upon the withdrawal of said bayonet assembly to preclude the force ful ejection of either the bayonet assembly or fluid from the casing. v

,7. 'Ihe combination with a piece of electrical apparatus including adielectric fluid containing casing provided withia line terminal, of a bayonet type oil circuitbreaker, said circuit breaker comprising a pair of cooperating elements one of which is a support fixedly positioned on the casing independently of the line terminal and the other of .which'is a bayonet assembly removably insertible into said support, said support having portions within and without the casing, the portion without the casing having an axial bore for receiving said bayonet assembly and the portion within the casing comprising a tubular element formed of insulating material projecting below the level of fluid in the casing, a pair of spaced contact receiving apertures in the wall of said tubular element disposed below the level of fluid in the casing, a pair of electrical contacts slidably receivable in said apertures respectively electrically connected with the line terminal and the piece of electrical apparatus, resilient means for urging said contacts toward the axis of said tubular element, said bayonet assembly comprising an insulating member, a pair of spaced electrical contacts on said member, a fusible current carrying element connecting said pair of electrical contacts on said member, and an operating handle on said bayonet assembly providing means by which said i i Z bayonet assembly may be inserted into or removed from said support to effect the selective closing and opening of said circuit breaker comprising a pair of cooperating elements one of which is a support fixedly positioned on the casing independently of the line terminal and the other of which is a bayonet assembly removably insertible into said support, said support having portions within and without the casing, the portion within said casing comprising a tubular clement formed of insulating material projecting below the level of fluid in the casing, a pair of spaced contact receiving apertures in the wall of said tubuar element disposed below the level of fluid in the casing, a pair of electrical contacts slidably receivable in said apertures and respectively electrically connected with the line terminal and the piece of electrical apparatus, resilient means for urging said contacts toward the axis of said tubular element, said bayonet assembly comprising a tubular member formed of insulating material having a diameter which is slidably receivable within said tubular element, a pair of spaced fixedly positioned contacts on said tubular member, a fusible element connecting said last named pair of fixedly positioned electrical contacts on said tubular member, a deformable resilient sleeve element on said bayonet assembly, and a rockable operating handle on said bayonet assembly provided with actuating means to selectively compress said yieldable rubber sleeve element into hermetic sealing pressure with said support or release the sealing pressure between said sleeve and said support when said bayonet assembly is in circuit making position.

9. The combination with a piece of electrical apparatus including a dielectric fluid containing casing provided with a line terminal, of a bayonet type oil circuit breaker, said circuit breaker comprising a pair of cooperating elements one of which is a support fixedly positioned on the casing independently of the line terminal and the other of which is a bayonet assembly removably inser-tible into said support, a tubular element formed of insulating material attached to said support and projecting below the level of fluid within said casing, a pair of spaced electrical contacts on said tubular efement, disposed below the level of fluid in said casing and respectively and electrically connected with the line terminal and the piece of electrical apparatus, said bayonet assembly comprising a tubular insulating member, slidably receivable in said tubular element, a pair of spaced electrical contacts on said tubular member, a fusible element connecting said pair of electrical contacts on said tubular member, a deformable resilient rubber sleeve element, a fixedly positioned stop on one end of said sleeve element, a movable stop at the other end of said sleeve element, and a rockably mounted operating handle having a cam surface engageable with said movable stop to selectively effect the compression of said deformabie element into sealing relationshipwith said support when said bayonet assembly is in circuit closing position and releasable to break the sealing engagement between said bayonet assembly and said support to permit the ready withdrawal of said bayonet assembly to break the aforementioned circuit.

10. The combination with a piece of electrical apparatus including a dielectric fluid containing casing provided with a line terminal, of a bayonet type oil circuit breaker, said circuit breaker comprising a pair of cooperating elements one of which is a tubular support fixedly positioned on the casing above the level of fluid therein and independently of the line terminal and the other of which is a bayonet assembly removably insertible into said tubular support, a vent passage in said tubular support dis posed above the level of fluid in the casing serving to establish open communication between the interior of the casing and the hollow central portion of said tubular support, an insulating element of tubular form projecting inwardly from said tubular support and having a portion thereof disposed below the level of fluid in the casing, a pair of spaced electrical contacts positioned in the wall of said tubular element below the level of fluid in the casing, said bayonet assembly comprising a tubular insulating member, a fusible bridging contact element on said tubular member connecting said spaced electrical contacts on said element when said bayonet assembly is in operating position within said support, a deformable resilient sleeve element on said bayonet assembly, and manually operable means for deforming said sleeve element to effect a sealing connection between said bayonet assembly and said support when said bayonet assembly is in operating position within said support, said vent passage serving to relieve the internal pressure generated in the casing by the rupture of said fusible bridging element under excessive load conditions to preclude the forceful ejection of either the bayonet assembly or fluid upon the breaking of the sealing connection between said bayonet assembly and said support.

11. The combination with a piece of electrical apparatus including a dielectric fluid containing casing provided with a line terminal, of a bayonet type oil circuit breaker, said circuit breaker comprising a pair of cooperating elements one of which is a tubular support fixedly positioned in sealing contact with the casing above the level of fluid therein and independently of the line terminal and the other of which is a bayonet assembly removably insertible into said support, a vent passage in said tubular support disposed above the level of fluid in the casing serving to establish open communication between the interior of the casing and the hollow central portion of said tubular support, a tubular element formed of insulating material projecting from said tubular support and having a portion thereof disposed below the level of fluid in the casing, a pair of spaced electrical contacts on said tubular element disposed below the level of fluid in the casing, said bayonet assembly comprising a tubular member formed of insulating material, a pair of spaced electrical contacts on said tubular member, a fusible current carrying element electrically connecting said last named contacts and serving to establish an electrical connection between the contacts on said tubular element when said bayonet assembly is in operating position within said support, a deformable resilient sleeve element on said bayonet assembly, a manually operable means for deforming said sleeve element to effect a sealing connection between said bayonet assembly and said tubular support when said bayonet assembly is in operating position within said tubular support and passages in said bayonet assembly establishing open pressure transmitting communication between the interior of the casing and the inner surface of the said deformable resilient sleeve member through the tubular member of said bayonet assembly to augment the mechanical sealing pressure of said deformable resilient sleeve with fluid pressure resulting from the rupture of said fusible current carrying element topreclude the forcible ejection of said bayonet assembly from said support under the tremendous instantaneous pressure resulting from the rupture of the fusible element.

12. The combination with a piece of electrical apparatus including a dielectric fluid containing casing provided with a line terminal, of a bayonet type oil circuit breaker, said circuit breaker comprising a pair of cooperating elements one of which is a tubular support fixedly positioned on the casing independently of the line terminal and the other of which is a bayonet assembly removably insertible into said tubular support, a vent passage in said tubular support disposed above the level of fluid in the casing to establish open communication between the interior of the casing and the hollow central portion of said tubular support, a tubular element formed of insulating material projecting from said tubular support and having a portion thereof disposed below the level of fluid in the casing, a pair of spaced electrical contacts positioned in said tubular element below the level of fluid in the casing, said bayonet assembly comprising a tubular member formed of insulating material, a pair of electrical contacts on said tubular member adapted to contact said first named electrical contacts when said bayonet assembly is in operating position in said tubular support, a fusible element electrically connecting said contacts on said tubular member, a deformable resilient sleeve element on said bayonet assembly, manually operable means for deforming said sleeve element to effect the application of sealing pressure between said bayonet assembly and said tubular support when said bayonet assembly is in operating position within said tubular support, and a passage in said bayonet assembly establishing communication between the interior of the casing and the inner surface of said deformable sleeve element through the tubular member of said bayonet assembly whereby the mechanical sealing pressure of said deformable sleeve is augmented by the tremendous instantaneous pressure resulting from the rupture of said fusible element under excessive load conditions to preclude the forcible ejection of said bayonet assembly from said tubular support, and venting passage serving to relieve the internal pressure in the casing upon the unsealing of the same to preclude the forcible ejection of fluid therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 1,058,143 Bitter et al. Apr. 8, 1913 2,281,073 Leonard Apr. 28, 1942 2,294,766 Williams Sept. 1, I942 2,351,969 Hurst June 20, 1944 2,421,236 Bennett May 27, 1947 2,663,825 Amundson Dec. 22, 1953 

